1598 NOTES has been extended to polar media with some success by Buckingham.I2 However, the necessary data are not yet available for hydrogen fluoride systems, and we have not attempted any correlations with such theory. I t is obvious that the effects are small and do not involve the formation of any new bonds. Indeed, the highly symmetrical ground states are essentially unperturbed. A t the temperature a t which the Raman spectra are observed, a significant number of vibrationally excited states are occupied and it is not clear to what extent these affect the observed band positions even for the pure materials. We believe such slight shifts as are observed in solution can be rationalized in terms of the effect of the dipole oriented atmosphere provided by the solvent on the polarizability ellipsoid associated w;th each Raman band, but no detailed analysis is yet available.
Acknowledgment.-One of the authors (B. F.) is indebted to the International Atomic Energy Agency, Vienna, A4ustria,and to the Nuclear Institute, "Josef Stefan," Ljubljana, Yugoslavia, who jointly granted a one-year fellowship. We thank L. Quarterman for the supply of lowconductivity hydrogen fluoride and H. Selig for highpurity rhenium and osmium hexafluorides. (12) A. D. Buckingham, Pvoc. Roy. SOC.(London), A248, 169 (1957).
Inorganic Chemistry reagent grade acetonitrile and Eastman Organic Spectrograde nitromethane were used as solvents for spectral and conductance studies. Conductance Measurements.--Molar conductivities of the complexes in both acetonitrile and nitromethane \yere measured with a Model R C 16B2 conductance bridge manufactured by Industrial Instruments, Inc. h dip type cell with a cell constant of 0.1 cm-' was used. Spectral Measurements.-Infrared spectra of Xujol mulls and KBr pellets of the complexes were recorded with a Beckman IR-7. T'isible and ultraviolet spectra were recorded with a Beckman Model DK-2B. Analyses.-Carbon, hydrogen, and nitrogen analyses were performed by Galbraith Laboratories, Knoxville, Tenn. Preparation of Complexes. (1) MoOC13.0MPA.-h alcoholic solution of MoOC13 mas prepared by dissolving 1.1g (0.0046 mole) of MoC16 in 30 ml of anhydrous ethanol.6 Reaction occurs immediately t o give a green solution of MoOC13. Addition of 2.1 g of OMPA (0.007 mole) caused a pale green solid to precipitate from solution. The product was filtered and washed with ether. Anal. Calcd for M o O C l ~ . [ C ~ H z ~ ~ ~ 4 0 3C, P z 19.9; ]: H, 4.i7; N, 11.1. Found: C, 19.3; H,4.89; K, 11.1. A Mechrolab osmometer was used to obtain the molecular weight of MoOC13 * OMPA in acetonitrile a t 37". Measurements were made for 0.02-0.09 X solutions. Anal. Calcd for h l o O C l ~[C8H2&403P2] . : mol wt, 505. Found: mol wt, 470 i 30. Molar conductance values-of 14 and 7 cm2 ohm-' mole-' were M solutions of h*foOc&OMPA in obtained a t 23" for 1 X nitromethane and acetonitrile, respectively. (2) lJ02(C104)z~30MPA.-0ne gram (0.002 mole) of UOz(C10a)z.4Hz0 was dehydrated w-ith 5 ml of 2,2-dimethoxypropane for 1 hr. Three grams (0.01 mole) of OMP.1 was added to the resulting solution. Some precipitation occurred about 1 min after adding OMPA. Anhydrous ether was added to precipitate additional product. An yield (2.1 g ) of LOz(Cl04)z.30MPA4was obtained. Anal. Calcd for UO~[CSH~~~\'~O~P~]~(CIO~)~: C, 21 .i; H , 5.42; N, 12.6. Found: C , 22.0; H, 5.61; N, 12.5. A molar conductance value of 162 cmz 0hm-I mole-' was obsolution of UOz(C104)2.30MPA in tained for a 9.6 X nitromethane a t 23 O. (3) Th(C104)4.40MPA.-Hydrated Th(C104)4.6Hz0 (0.74 g, 0.001 mole) was dissolved in 10 ml of acetone. A 5 : 1 ratio of OMPA (1.43 g) was added t o the solution. A white solid precipitated from solution when anhydrous ether was added. The product mas washed several times with ether and dried under vacuum for 2 hr a t room temperature. A 977, yield was obtained. Anal. Calcd for Th[CsH2403P?]4(C104)4: C, 21.6; H, 5.41; N, 12.6. Found: C, 21.7; H, 5.i5; N, 12.3. T h e molar conductance was measured a t 23' for a 8.89 X 10-4 ill nitromethane solution and found to be 315 cm2 ohm-' mole-'. 9
CONTRIBUTION FROM THE DEPARTMENT OF CHEMISTRY, VANDERBILT UNIVERSITY,SASHVILLE, TENNESSEE 37203
T h e Donor Properties of P y r o p h o s p h a t e Derivatives. V. Complexes of MoOCl,, UO?+, a n d Th4+ w i t h Octamethylpyrophosphoramide BY MELVIND.
JOESTEN
Received February 24, 1967
We have previously reported the isolation and characterization of complexes of octamethylpyrophosphoramide (OMPA) with over 30 metal The general characteristics of OMPA as a ligand are (1) formation of air-stable complexes with metal ions, (2) coordination as a bidentate ligand through phosphoryl oxygens, (3) enhancement of the maximum coordination number of the metal ion, and (4) essentially electrostatic bonding to metal ions as shown by low Dp and 0parameters toward Ni(I1). The purpose of the present study was to determine whether OMP-4 could form stable complexes with oxycations and T h 4 f . Experimental Section Chemicals.-Molybdenum pentachloride was obtained from K and K Laboratories and used without further purification. Both hydrated uranyl perchlorate and hydrated thorium perchlorate were obtained from G. Frederick Smith Chemical Co. Fisher (1) M. D. Joesten and K . M. Nykerk, Inorg. Chem., 3, 548 (1964). (2) C. J. Popp and M. D. Joesten, ibid., 4, 1418 (1965). (3) M. D. Joesten and J. F. Forbes, J. Am. Chem. Soc., 88, 5465 (1966). (4) M. D. Joesten and R. A. Jacob, Abstracts, 152nd National Meeting of the American Chemical Society, New York, N. Y.,Sept 1966; "The 'Chemistry of Lanthanide and Actinide Elements," Advances in Chemistry Series, American Chemical Society, Washington, D. C., in press.
Results and Discussion MoOC13,0MPA.-The complex is a nonelectrolyte and monomeric in acetonitrile (Experimental Section). The ultraviolet and visible absorption peaks for MoOC13.0MPA (Table I) are similar to those reported for other adducts of M o O C ~ ~ .On ~ ~the ' basis of spectral assignments made by previous workers for the l l ; I 0 0 3 + i ~ n ,the ~ ,bands ~ for MoOC13.0MPAa t 13,700 and 19,000 cm-1 have been assigned as the transitions (5) (6) (7) (8) (9)
W. Wardlaw and H. Webb, J . Chem. Soc., 2100 (1930). D. A. Edwards, J. Inoug. h'ucl. Chcm., 27, 303 (1965). S. M. Horner and S. Y.Tyree, Jr., Inovg. Chem., 2 , 568 (1963). H. B. Gray and C. R. Hare, ibid., 1,363 (1962). K. Feenan and G. W.A. Fowles, i b i d . , 4, 310 (1965).
NOTES 1599
Vol. 6, No. 8, August 1967 TABLE I ULTRAVIOLET AND VISIBLE SPECTRAL DATAI N ACETONITRILE Compound hax, mrc (“1) e MoOC13.OMPA 240 (41,700) 4870 306 (32,700) 2900 447 (22,400) 43 732 (13,650) 21
2Bz+ 2E(1)and 2Bz + 2B1. The bands a t 32,700 and 41,700 cm-l are charge-transfer bands, as indicated by their high molar absorptivities. The Mo=O stretching frequency appears a t 990 cm-l in MoOC18. OMPA, which is slightly higher than Mo=O stretching frequencies previously reportedS6 These include 965 cm-l for [Mo0C1~]~-, 979 cm-I for MOOC13.bipy, 967 cm-1 for MoOCl~.2(C6H~)3PO, and 980 cm-l for MoOC13.2CH8CN. The decrease in the P=O stretching frequency and the increase in the P-N stretching frequencies are support for coordination of molybdenum with the phosphoryl oxygens. I n conclusion, the experimental evidence supports the presence of six-coordinate molybdenum in a molecular complex in which [Mo=OJ3+ is attached t o three chlorides and two phosphoryl oxygens. UOz(C104)~30MPA.-At present, there is general agreement that UOzZ+ can form complexes with four, five, and six donor sites.1° The molar conductance of uO~(c104)2~30MPA in nitromethane is in the range expected for 2 : 1 e1ectrolytes.l’ The shifts in the P=O and P-N stretching frequencies (Table 11) are in the direction expected for formation of chelate rings through the phosphoryl oxygens. It was not possible t o assign a U=O stretching frequency since this occurs in the same region as P-N1 (900-1000 cm-l). On the basis of these experimental data, a likely structure for UOZ(C104)2.30MPAis one in which the phosphoryl oxygens from the OMPA molecules form chelate rings in TABLE I1 INFRARED SPECTRAL ASSIGNMENTS (C M - ’ ) ~ Band P=O P-NI P-Nz P-0-P Metal-0 Clod-
OMPA
Th(ClO4)r. 40MPAb
1238s 988, 756 w 915s
1140 s 995 s 790, 765 w 905 s
1160 s, 1185 sh 1000 s 795 w, 770 m, 775 m 920 s
1090 s
1090 s
... ...
...
UOz(C104)z~ 30MPAC
...
MoOCla * OMPAc
1188 s 1018 m 795 w 910 s 990 s
...
Intensities of bands: s, strong; m, medium; w, weak; sh, shoulder. K B r pellet. Nujol mull. a
the equatorial positions around [O=U=O]2+. This would give a structure similar to that found for NaUO2( C ~ H 3 0 2 ) 3except ~~ that the chelate rings involving OMPA molecules would be puckered. Th(C104)4*40MPA.-The elemental analysis, infrared spectral data, and conductivity measurements support the assignment of a coordination number of eight to Th4+. The decrease in the P=O stretching frequency (98 em-’) as well as the increase in P-N1 and P-N2 stretching frequencies are support for co(10) A. E.Comyns, Chem. Rev., 60, 115 (1960). (11) N.S. Gill and R. S. Nyholm, J . Chcm. Soc., 3997 (1959). (12) W.H.Zachariasen and H. A. Plettinger, Acta Curst., 18,526 (1959).
ordination of the T h 4 + to the phosphoryl oxygens of OMPA. The acetylacetonate (acac) complex of Th4+, Th(acac)4, has an Archimedian antiprismatic structure.l 3 The ability of OMPA to coordinate as a bidentate ligand and the similarity in stoichiometry and ring size in the systems Th(C10&.4OMPA and Th(acac)4 lead us to predict an Archimedian antiprismatic structure for Th(C104)4*40MPA. (13) D. Grdenic and B. Matkovic, Nalzrue. 182,465 (1958).
DIVISIONOF ENGINEERING DEPARTMENT OF CHEMISTRY, BROWNUNIVERSITY, PROVIDENCE, RHODEISLAND02912 CONTRIBUTION FROM
THE
AND THE
The Preparation and Electrical Properties of Niobium Selenide and Tungsten Selenide‘ BY R . KERSHAW, M. VLASSE,AND A. WOLD
Received February 27, 1967
Revolinsky, et a1.,2have shown that NbSez has both a hexagonal two-layer structure of the NbSz type and a four-layer structure of a new structure type. The structures are composed of trigonal prismatic NbSez slabs. The anions are arranged as two parallel close-packed sheets with the metal atoms occupying trigonal prismatic sites. The qrrangement of the cations with respect to each other is that of a close-packed hexagonal layer. The NbSe2 slabs can be stacked in a number of different ways with one, two, three, four, or six NbSez layer sequences being the usual arrangements. Figure l a illustrates the two-layer sequence for NbSez. For both the two-layer (e) and the four-layer (6) structures, the coordination within the “molecular” slabs is trigonal prismatic. Beerntsen, et al.,3 have shown that the two-layer NbSez structure is superconducting. The high-temperature four-layer modification was also superconducting. Revolinsky, et a1.,2 reported that the superconducting transition temperature for the two-layer phase was 7’K. Brixner4 has described the preparation, structure, and thermoelectric properties of WSe2. WSez is a rather well-behaved semiconductor with a relatively low electrical conductivity (increasing with temperature) and a high Seebeck coefficient. Figure l b shows a two-layer sequence for WSe2. Both WSez and NbSez crystallize in the D6h4-P6/mmc space group and have exactly the same anion packing. It can be seen from Figure 1 that only the cation arrangement differs. (1) This work has been supported by ARPA and Grant No. A F 33(615)3844. (2) E. Revolinsky, G. A. Spiering, and D. J. Beerntsen, J. Phys. Chem. Solids, 86, 1029 (1965). (3) D. J. Beernsten, G. A. Spiering, and C. H. Armitage, IEEE Trans. Aerospace, 8 , 816 (1964). (4) L. H.Brixner, J . Inorg. Nucl. Chem., 24, 257 (1962).
